This invention relates generally to industrial process control systems having process instruments. More particularly, the present invention relates to process instruments having local display means for outputting information relating to functions of the process instrument.
Process instruments are used to monitor process variables, such as pressure, temperature, flow and level, of process fluids used in industrial processes. For example, process transmitters are typically employed in industrial manufacturing facilities at multiple locations to monitor a variety of process variables along various production lines. Process transmitters include sensors that produce an electrical output in response to physical changes in the process. For example, pressure transmitters include pressure transducers that produce an electrical output as a function of the pressure of a process fluid, such as in water lines, chemical tanks or the like. Each process transmitter also includes transmitter electronics for receiving and processing the electrical output of the sensor so that the transmitter and process can be monitored remotely or locally. Remotely monitored transmitters include electronics that transmit the electrical output over a control loop or network to a central monitoring location such as a control room. With remote monitoring, the process can be automatically regulated from the control room by including automated switches, valves, pumps and other similar components in the process control system and the control loop. Locally monitored transmitters include displays, such as liquid crystal display (LCD) screens, that show the electrical output at the site of the process transmitter. With local monitoring, the process can be manually regulated in the field by operators reacting to information obtained from the transmitter.
For both locally and remotely monitored transmitters, it is desirable to view information relating to operation of the process and the transmitter at the site of the transmitter. For example, operators and repair personnel often require real-time information such that obtaining information from a control room is inconvenient. As such, transmitters are capable of being equipped with local displays, which typically comprise an LCD. Conventional displays are limited in the variety of information they are capable of displaying. Furthermore, transmitter electronics typically include a transmitter-specific interconnection that allows an LCD module to be linked to the electronics using various types of mechanical and electrical connections. LCD modules also vary in size of the display, power requirements and software interfaces. This divergence in display technology results in increased manufacturing costs as many different LCD modules need to be designed and built or purchased. There is, therefore, a need for a local display means that is universally applicable across a wide variety of transmitter types and electronics platforms.